Libertarian writer Jesse Walker is dismissive of the latest FBI report on "active shooters". This is not the same thing  as mass shootings, or mass murders, and only by using the FBI's definition and list of cases can you say that they're "on the rise."  [The FBI Says 'Active Shooter Incidents' Are On the Rise. What Does That Mean? | September 24, 2014]

But I wanted to know what  the racial breakdown of these shootings is, in terms of race of shooters and victims.

Well, here is absolutely all that the FBI has to say about that:

The shooters victimized young and old, male and female, family members, and people of all races, cultures, and religions.[PDF p. 8]

Otherwise, there is no mention of the race of the shooters, the race of the victims, or any racial motive they may have had.